Sorry for the confusion, but it is part of the game! As Linkin said, different people use different ‘signs’ for their tabs. Hopefully, there will be a legend with a tab to say what each sign or symbol means. If not, sometimes all you can do is listen to the song and try to figure out what it means.

Also, the symbol I see most often for a ghost note is x. Sometimes the () can mean this is a different fret you can use if it works better for you. I have not seen the rr before! This is why every tab should have a legend! Cheers.

x is also often a dead note. It's much more common in guitar tabs though. Sort of like a rythmic thump where you put your left hand over your fretboard lightly so you don't fret anything while plucking a string.